The Go Foil carbon mast is 14mm thick, strong and fast and not too heavy considering fuselage built in.

I agree a universal mast around 14-15mm is needed, 19mm is thick for winging as in flat water drag is your enemy, there are wings of other brands I'd like to try as most brands have that one standout wing

Hey I'm new here but couldn't help chiming in on this discussion. I've needed a reason to do a simple study on mast thickness and this forum finally gave me that reason!

Based on some of the comments here I ran a study in XFLR with my Inde wingset as a baseline, and some different mast sections through a full operating range of speeds. XFLR5 is what I use to do foil design, it's great, its free, and its results are the best out of the handful of CFD panel codes out there. Results are for the full 3D wingset with viscosity included.

The results have following constants:
Chord length: 110mm
Immersed mast section: 380mm (half of a 75cm mast)
NCRIT 1.5 (turbulent flow)
1100cm2 wing and 200cm2 stabilizer
85kg rider
The section is a NACA 6 series scaled to 11% and 17% which results in a 12.3mm and 19mm thickness at this chord length but the section shape other than thickness is the same.
0 degree yaw (important)

Just now realizing I can't post photos, I'll share some interesting graphs once I can.

At 10knots
NACA 64A-011 (12.4mm thick)
Total drag: 52.5N
Mast % of total: 10.48%
NACA 64A-017 (19mm thick)
Total drag: 53.8N
Mast % of total: 12.64%
Difference: 2.16%

At 20knots
NACA 64A-011 (12.4mm thick)
Total drag: 88N
Mast % of total: 18.2%
NACA 64A-017 (19mm thick)
Total drag: 94N
Mast % of total: 23.4%
Difference: 5.22%

So at 0 degrees yaw 2-5% change in overall drag doesn't seem like much. 23% of the total foil drag at speed, definitely seems like a lot though. All of these results change as soon as the foil is yawed though, when the mast has an angle of attack. When your roll angle is non zero, so is your yaw angle, so the amount of time your foil is operating in this condition is relatively small. With more lift, there is more drag, so as soon as the mast is generating lift, the difference between these numbers will go up.

Haven't thought about mast lift before but I'm surprised how stable our foils are at speed. I remember with the old windsurfer with a center board how at speed the board would tilt and throw you off if the cboard was down. Would expect as we roll in a turn to get more upsetting lift from the mast than seems to happen. Maybe its countered by the foil and tail.

Select to expand quote

Fishdude said..

Hdip said..

Fishdude said..
Does the depth of the water change the amount of drag?
A little off topic but in the same realm. Putting the additional longer mast drag aside... Would a foil at 90cm depth have more resistance to flying (taking off) than the same foil at 60cm depth?

James Casey and Dave Kalama are using shorter masts in downwinds to make paddling up easier.

Yeah, I see that, and others have said this too. My question WHY does a shorter mast make for earlier take off?
Is their earlier flying ONLY due to having 50% less mast in the water at take off? (60cm vs 90cm mast). Or does the foil being 30cm deeper,(under more pressure) also add more resistance to moving through water?

Easier takeoff is not really due to less drag. It is because there is more wave energy nearer the surface.

Select to expand quote

indefoiler said..
Hey I'm new here but couldn't help chiming in on this discussion. I've needed a reason to do a simple study on mast thickness and this forum finally gave me that reason!

Based on some of the comments here I ran a study in XFLR with my Inde wingset as a baseline, and some different mast sections through a full operating range of speeds. XFLR5 is what I use to do foil design, it's great, its free, and its results are the best out of the handful of CFD panel codes out there. Results are for the full 3D wingset with viscosity included.

The results have following constants:
Chord length: 110mm
Immersed mast section: 380mm (half of a 75cm mast)
NCRIT 1.5 (turbulent flow)
1100cm2 wing and 200cm2 stabilizer
85kg rider
The section is a NACA 6 series scaled to 11% and 17% which results in a 12.3mm and 19mm thickness at this chord length but the section shape other than thickness is the same.
0 degree yaw (important)

Just now realizing I can't post photos, I'll share some interesting graphs once I can.

At 10knots
NACA 64A-011 (12.4mm thick)
Total drag: 52.5N
Mast % of total: 10.48%
NACA 64A-017 (19mm thick)
Total drag: 53.8N
Mast % of total: 12.64%
Difference: 2.16%

At 20knots
NACA 64A-011 (12.4mm thick)
Total drag: 88N
Mast % of total: 18.2%
NACA 64A-017 (19mm thick)
Total drag: 94N
Mast % of total: 23.4%
Difference: 5.22%

Interesting, thanks

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indefoiler said..
So at 0 degrees yaw 2-5% change in overall drag doesn't seem like much. 23% of the total foil drag at speed, definitely seems like a lot though. All of these results change as soon as the foil is yawed though, when the mast has an angle of attack. When your roll angle is non zero, so is your yaw angle, so the amount of time your foil is operating in this condition is relatively small. With more lift, there is more drag, so as soon as the mast is generating lift, the difference between these numbers will go up.

Super interesting calculation thanks indefoiler! I am curious about the drag with other values of yaw.. 1 to 5 degrees for example? Because as you said the time spend at 0 degree of yaw is very small.

Select to expand quote

emmafoils said..

Fishdude said..

Hdip said..

Fishdude said..
Does the depth of the water change the amount of drag?
A little off topic but in the same realm. Putting the additional longer mast drag aside... Would a foil at 90cm depth have more resistance to flying (taking off) than the same foil at 60cm depth?

James Casey and Dave Kalama are using shorter masts in downwinds to make paddling up easier.

Yeah, I see that, and others have said this too. My question WHY does a shorter mast make for earlier take off?
Is their earlier flying ONLY due to having 50% less mast in the water at take off? (60cm vs 90cm mast). Or does the foil being 30cm deeper,(under more pressure) also add more resistance to moving through water?

Easier takeoff is not really due to less drag. It is because there is more wave energy nearer the surface.

Got it, Thanks. Makes sense, I should have figured that out but my brain just went in a different direction.

Let's assume all 3 approaches (frontal surface area, nasa sim and XFLR5) are indeed correct and the drag difference is roughly 5%. Does a 5% drag difference give a 5% difference of glide or power input when pumping? Is there an equation linking drag and glide or drag and energy input?
Also, the relationship between power output and time delivering that power for the human body is not linear, as the wakethief shows in his pumping forever video, a little power input change has a drastic effect on the time able to sustain it.
Maybe the relationship between drag and sensation in the water is non linear and that 5% feels like much more, as some people like Kane tend to observe.

Select to expand quote

foilstate said..

indefoiler said..
So at 0 degrees yaw 2-5% change in overall drag doesn't seem like much. 23% of the total foil drag at speed, definitely seems like a lot though. All of these results change as soon as the foil is yawed though, when the mast has an angle of attack. When your roll angle is non zero, so is your yaw angle, so the amount of time your foil is operating in this condition is relatively small. With more lift, there is more drag, so as soon as the mast is generating lift, the difference between these numbers will go up.

Super interesting calculation thanks indefoiler! I am curious about the drag with other values of yaw.. 1 to 5 degrees for example? Because as you said the time spend at 0 degree of yaw is very small.

I could definitely run that calculation, the wingset lift will change completely as well once yawed. The issue is I think each section would find equilibrium at a different yaw angle and I don't know what those angles are for each section. So I'm not sure how valid of a comparison that would be.

Select to expand quote

foilstate said..
Let's assume all 3 approaches (frontal surface area, nasa sim and XFLR5) are indeed correct and the drag difference is roughly 5%. Does a 5% drag difference give a 5% difference of glide or power input when pumping? Is there an equation linking drag and glide or drag and energy input?
Also, the relationship between power output and time delivering that power for the human body is not linear, as the wakethief shows in his pumping forever video, a little power input change has a drastic effect on the time able to sustain it.
Maybe the relationship between drag and sensation in the water is non linear and that 5% feels like much more, as some people like Kane tend to observe.

Velocity is squared in the kinetic energy and drag equations so that would line up with non-linear power input. Not sure how you equate the two though. Maybe it's just that drag goes up with the square of velocity?

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foilstate said..

Maybe the relationship between drag and sensation in the water is non linear and that 5% feels like much more, as some people like Kane tend to observe.

I have no data to back this but i think it is probably correct.
Foil pumping is just on the edge of "doable" so i find it very likely that even a 5% increase in drag will put you on the wrong side of the line and doing the Titanic real quick.

Select to expand quote

Fishdude said..

Hdip said..

Fishdude said..
Does the depth of the water change the amount of drag?
A little off topic but in the same realm. Putting the additional longer mast drag aside... Would a foil at 90cm depth have more resistance to flying (taking off) than the same foil at 60cm depth?

James Casey and Dave Kalama are using shorter masts in downwinds to make paddling up easier.

Yeah, I see that, and others have said this too. My question WHY does a shorter mast make for earlier take off?
Is their earlier flying ONLY due to having 50% less mast in the water at take off? (60cm vs 90cm mast). Or does the foil being 30cm deeper,(under more pressure) also add more resistance to moving through water?

I think it might have been discussed elsewhere as well - but essentially the reason why a shorter mast is easier to launch is because of the foils surface interaction, more than the amount of mast in the water. The reason for this is that the foil displaces and pushes water up towards the surface when moving through the water. The closer the foil is to the surface the less water the foil has to displace (air is lighter than water) and the less draggy it will feel. You can see it on some of the pump videos in glassy conditions, the water displaces up and creates a wake behind the mast.

When you are learning to pump the same applies. The higher you fly the more efficient the pump becomes, because you are having less amount of water to displace.

To get good at pumping, a good trick is to force your self to look up. We all tend to look down and gauge our ride-height with a visual estimate, but if you look up, it forces you to feel the extra glide which occurs when your foil is closer to the surface. It's quite significant, and it's a great way to experience the reduction in drag and getting better pumping results.

Select to expand quote

\PeterP said..

Fishdude said..

Hdip said..

Fishdude said..
Does the depth of the water change the amount of drag?
A little off topic but in the same realm. Putting the additional longer mast drag aside... Would a foil at 90cm depth have more resistance to flying (taking off) than the same foil at 60cm depth?

James Casey and Dave Kalama are using shorter masts in downwinds to make paddling up easier.

Yeah, I see that, and others have said this too. My question WHY does a shorter mast make for earlier take off?
Is their earlier flying ONLY due to having 50% less mast in the water at take off? (60cm vs 90cm mast). Or does the foil being 30cm deeper,(under more pressure) also add more resistance to moving through water?

I think it might have been discussed elsewhere as well - but essentially the reason why a shorter mast is easier to launch is because of the foils surface interaction, more than the amount of mast in the water. The reason for this is that the foil displaces and pushes water up towards the surface when moving through the water. The closer the foil is to the surface the less water the foil has to displace (air is lighter than water) and the less draggy it will feel. You can see it on some of the pump videos in glassy conditions, the water displaces up and creates a wake behind the mast.

When you are learning to pump the same applies. The higher you fly the more efficient the pump becomes, because you are having less amount of water to displace.

To get good at pumping, a good trick is to force your self to look up. We all tend to look down and gauge our ride-height with a visual estimate, but if you look up, it forces you to feel the extra glide which occurs when your foil is closer to the surface. It's quite significant, and it's a great way to experience the reduction in drag and getting better pumping results.

I think pumping and takeoff work a bit differently regarding mast length.

As far as I've read, the wings of a hydrofoil actually get less efficient closer to the surface. I believe the reduction in mast drag makes up for this but am really not educated enough to say definitively.

On takeoff my theory relates to how it effects the trim of the board. I experience more front foot pressure or a higher upward pitching force on a longer mast.

For a flat takeoff, your center of gravity needs to align vertically with the center of lift. the wings also need angle of attack.
20deg Aoa on a 100cm2 mast will place the wings much farther forward than 20deg on a 60cm mast. You should have to lean to make up for this, which is what I experience.
This difference in fore-aft position under the board is even more relevant when pumping on to foil and accelerating after the initial lift. on a long mast either the foil, board, or both have to swing farther under you. This probably makes it harder for your body to pump and control. I usually end up too far back on long masts and end up stalling the foil before getting enough speed to swing it under me.

This is all very dynamic but common sense is less CoG movement is probably more efficient.

Downwind a short mast brings the foil into a higher energy part of the wave and can get the wings close to the surface faster, where there's even more power and less drag.

Mast stiffness vs drag, comparing the takuma alu (75cm long, 15.5mm thick) and cedrus (77cm long, 19mm thick) mast, this time in the water. Proning the cedrus, using my 4'6 appletree board, kujira 1210, 178 tail no shim, stock fuse, knee to waist high clean waves, clean water. Going back and forth with the 2 masts, everything else being equal.

Stiffness : The takuma alu feels okay but could be better, a bit wobbly on the pump if not pumped straigth down, and some delay in the turns (spring effect). The cedrus is as stiff as it gets, no wobble, direct feedback, less delay in turns, absolute control.

Drag : The cedrus feels somewhere between 10 to 30% more draggy than the takuma alu. This drag feel translates directly to the same change on energy per pump and glide. Theorically it should be ~5% and maybe it is, but this is what it actually "feels" like in the water.
On high pumps with the wing close to the water surface, the drag feels about 10% more on the cedrus, on bottom turns full speed on the wave with the mast almost fully immersed, the drag feels about 30% more on the cedrus.
The result is that it kills the speed generated by either the wave or the pump, and the energy required to make it work is instantly noticeable. The sensation is comparable to having seaweed stuck in the fuse, as the nose of the board is pitching down when the speed increases. On the cedrus I can do a run of a few minutes on the kujira 1210 connecting waves with a major effort. On the takuma alu I can do 10 to 20 minutes runs with relative ease.

The difference of drag might be on the extreme end with the takuma foils, as everything is built around drag reduction. My try of the art999 on the 19mm thick axis alu mast did not shock me at all, so it might depend on the brand. Rider preference, rider weight, brand, wing size and discipline all play a huge role in the choices of gear, and I am sure the cedrus fits some cases perfectly.
The cedrus mast does not fit what I am searching for unfortunately, despite an amazingly built mast, ultra rigid and bullet proof for weight loads.

This drag difference is a major eye opener for me. This falls exactly in line with what Kane de Wilde has been saying. I am now curious to try a thinner mast than 15.5mm, while keeping a decent rigidity, and connect it to a kujira or art wing.
The slingshot plantasm, ono, signature,.. are thin and rigid. The challenge is to make the connection to the fuselage. I talked to stringy who can make sab/slingshot mast to takuma fuse.
Nolimitz seem to be okay rigid, 16mm, non interchangeable fuse connection.
Alchemy comes up with building blocks on the armstrong mast, could be a solution in the works.
If you know a viable solution, let me know!

Select to expand quote

FoilAddict said..

I think pumping and takeoff work a bit differently regarding mast length.

As far as I've read, the wings of a hydrofoil actually get less efficient closer to the surface. I believe the reduction in mast drag makes up for this but am really not educated enough to say definitively.

On takeoff my theory relates to how it effects the trim of the board. I experience more front foot pressure or a higher upward pitching force on a longer mast.

For a flat takeoff, your center of gravity needs to align vertically with the center of lift. the wings also need angle of attack.
20deg Aoa on a 100cm2 mast will place the wings much farther forward than 20deg on a 60cm mast. You should have to lean to make up for this, which is what I experience.
This difference in fore-aft position under the board is even more relevant when pumping on to foil and accelerating after the initial lift. on a long mast either the foil, board, or both have to swing farther under you. This probably makes it harder for your body to pump and control. I usually end up too far back on long masts and end up stalling the foil before getting enough speed to swing it under me.

This is all very dynamic but common sense is less CoG movement is probably more efficient.

Downwind a short mast brings the foil into a higher energy part of the wave and can get the wings close to the surface faster, where there's even more power and less drag.

This makes a lot of sense, and I haven't come across this theory before. Everyone kind of knows that a longer mast is more difficult to pump up on foil (whether wing or SUP) but from what I hear the general idea people seem to have is that shorter mast equals less stuff in the water and therefore less drag. But I think this explanation above (less CoG movement = more efficient) probably has a bigger effect than we think.

What length masts are you using for DW now Kane?

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FoilAddict said..
Slingshot carbon mast is incredible. Thinner at the bottom than any mast out there and very stiff. The Ono Foil mast is one of the best I've used, and is only 16mm thick so pretty fast. I liked my ride on the nolimitz, and the Armstrong is alright but could be a touch stiffer for big boards. Lift is too flexible for me.

the carbon used in a mast makes a huge difference, some race foil and prototype masts using nicer carbon are thinner AND stiffer than what we're riding now. Those masts would probably retail $2000+ though.

universal masts are the future, I would love to see a tapered one!
I find I notice the mast thickness drag most while pumping, and least while winging.
A longer mast probably isn't harder to takeoff because of the drag, it's more a combination of the foil's leverage in your board and how close the foil is to the surface power. Long masts tend to pitch up harder on takeoff, short masts take off very level. We tested this a while back with 2 identical setups on axis 930. One with a 70cm aluminum mast and one with an 85cm. SUP downwind I could get up in a few strokes on the short mast and a few minutes on the long mast. Almost exactly the same board, same fuse, front wing, tail, and track placement.

Kane you are absolutely right. I've got my hands on a custom racing mast from Fone built with high modulus carbon (adapted for cabrinha), 13.1cm chord and 14mm thick at the plate, 11.3cm chord and 13mm thick at the fuse, as rigid as a cedrus! Masts can be stiff and thin

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foilstate said..

as rigid as a cedrus! Masts can be stiff and thin

Yes, they can be stiff and thin but this comes at the expense of weight and cost because it is solid carbon and therefore requires more material and labor to layup. The challenge of multi-disciplinary optimization is discussed extensively on the blog of Project Cedrus. Nowhere on the site does it state that you can't have thin and stiff, but you can't have both those and low weight (and compatibility, and some of the other benefits). If top-end speed is more important than weight and cost, there are lots of stiffer racing masts out there. Project Cedrus was never intended to be a race mast, and was optimized for weight, stiffness, and compatibility.

Select to expand quote

BayAreaKite said..

foilstate said..

as rigid as a cedrus! Masts can be stiff and thin

Yes, they can be stiff and thin but this comes at the expense of weight and cost because it is solid carbon and therefore requires more material and labor to layup. The challenge of multi-disciplinary optimization is discussed extensively on the blog of Project Cedrus. Nowhere on the site does it state that you can't have thin and stiff, but you can't have both those and low weight (and compatibility, and some of the other benefits). If top-end speed is more important than weight and cost, there are lots of stiffer racing masts out there. Project Cedrus was never intended to be a race mast, and was optimized for weight, stiffness, and compatibility.

I have been hearing and reading about stiff and thin masts, but with most masts in the market being soft and thick it was hard to believe. Getting to use one in real life I now know it for a fact that it's possible. I wish there was a thin stiff universal mast out there, the cedrus I bought is unusable for me with that drag (that I thought would be negligeable). Hopefully we get one soon!

Im a few sessions on a Cedrus now, solely winging, and first and foremost - I definitely like it. The stiffness is absolutely an improvement on the wide span / high AR wings that I like riding. It is very noticeable in handling and pumping (vs Takuma and Lift masts that I know well). The build quality is also great.

I do not notice increased drag when I'm high on the foil, which is where I should be. That said, I do notice the drag when I botch a drop and come down low on the mast (obviously - since more mast in the water = more drag). If I come down low on the mast it means I have too much front foot pressure, but then the slowdown from the increased drag of the mast actually throws my weight forward even more and exacerbates the front foot pressure. I think I will be able to figure out how to correct this through (a) bumping the mast forward slightly and (b) self correcting my weighting to anticipate this.

For my riding, I think that the benefits will offset the drawbacks. There are some differences that will require me to compensate, but they are fairly predictable and can be adjusted for.

caveat that I have been trying new foils simultaneous with getting used to the Cedrus, so there are several variables that I'm working through. I can confidently say that my mast position isn't dialed in yet, and it could be complicating these early reads.

Select to expand quote

BayAreaKite said..

foilstate said..

as rigid as a cedrus! Masts can be stiff and thin

Yes, they can be stiff and thin but this comes at the expense of weight and cost because it is solid carbon and therefore requires more material and labor to layup. The challenge of multi-disciplinary optimization is discussed extensively on the blog of Project Cedrus. Nowhere on the site does it state that you can't have thin and stiff, but you can't have both those and low weight (and compatibility, and some of the other benefits). If top-end speed is more important than weight and cost, there are lots of stiffer racing masts out there. Project Cedrus was never intended to be a race mast, and was optimized for weight, stiffness, and compatibility.

I understand there have to be compromises, you cannot have it all.
But quite a few user reviews say that the Cedrus is too draggy to be truly enjoyable.

Glide (low drag) is such a big aspect of foiling...maybe the Cedrus design could be adapted to a narrower profile at the cost of some weight gain and less stiffness A new compromise.

Taper would be ideal but maybe it would make it too complex to build.

Thin and stiff are the main attributes, weight comes third and cost really doesn't seem to matter to foilers.. Even poor ones like me.Just don't buy food, loose weight and foil better !

I have a Cedrus, compared to the alu takuma you can feel the drag which is realy annoying especially at low speed for pumping.
On the wave the drag is not an issue for me. You definetly get more performance in the wave because of the stiffness.
I will try the Nolimitz soon, so i will be able to compare.

I think the Cedrus is good for winging or even sup or surf if pumping back out is not your main focus. Or for bigger guys.

For sup dw, in light conditions with the Takuma 1440, the alu is more efficient but if it is strong wind/big bumps then the control gets more important as you will go fast anyway, especialy with a smaller fornt wing.
So for me the Cedrus is not the best option, at least not for everything.

Thin masts are fun if they would be stiff enough and i,m afraid that with my 98kg thinner masts are pretty much an just theoretical thing.
I have an Cedrus for a month now with Sab foils and a Kujira 1210 and it feels a tiny bit slower as my Sab82mast, but also soo more controlled that the plusses outperform the light added drag.
I tried the Kujira 1210 with an alu mast, and that thing was twisting and bending like a Hula dancer. I rather have the added drag and being able to steer as all the uncontrolled bending.I can imagine that in the future you get masts that are trimmed to a certain rider weight.: thinner and maybe lighter for the Hobits flyweights and thicker and/or heavier for he bigger boned people.

I side by side tested Cedrus and NoLimitz (own both) with Axis 999 and 1099. Both surf foiling and wing foiling. I couldn't tell any difference in drag - and that's with a super low drag foil setup so it should be obvious if it was. The stiffness difference is immediately noticeable. I'm 100% back on Cedrus now.The Inde Foil study shows a 2-5% difference in total drag when going from 12mm to 19mm mast thickness. We are talking about 16mm vs. 19mm so much less difference. I think the extra drag on the cedrus could possibly just be in folks heads.

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jondrums said..
I side by side tested Cedrus and NoLimitz (own both) with Axis 999 and 1099. Both surf foiling and wing foiling. I couldn't tell any difference in drag - and that's with a super low drag foil setup so it should be obvious if it was. The stiffness difference is immediately noticeable. I'm 100% back on Cedrus now.The Inde Foil study shows a 2-5% difference in total drag when going from 12mm to 19mm mast thickness. We are talking about 16mm vs. 19mm so much less difference. I think the extra drag on the cedrus could possibly just be in folks heads.

haha If you decide to sell your No Limitz then let me know!

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jondrums said..
I side by side tested Cedrus and NoLimitz (own both) with Axis 999 and 1099. Both surf foiling and wing foiling. I couldn't tell any difference in drag - and that's with a super low drag foil setup so it should be obvious if it was. The stiffness difference is immediately noticeable. I'm 100% back on Cedrus now.The Inde Foil study shows a 2-5% difference in total drag when going from 12mm to 19mm mast thickness. We are talking about 16mm vs. 19mm so much less difference. I think the extra drag on the cedrus could possibly just be in folks heads.

I think Axis art need super stiff to mast to make it work so that is probably why. I actually like the cedrus on the art foils.
Now I'm using the new Axis carbone mast which is super stiff, seems stiffer than Cedrus but maybe a bit less responsive, I still need to do some tests.

But when using Kujira 1095, the difference between cedrus vs alu is noticeable for efficiency on the pumping, defintly not in my head for sure.

In the Project Cedrus episode of Progression Project podcast, Erik mentions that he pushes the mast far forward of his normal position, then offsets the increased lift of that mast position by reducing the tail shim (flatter tail). The flatter tail reduces drag to the point where he says the increased drag of the Cedrus is minimal. I'm experimenting with similar adjustments on my Cedrus x Takuma setup with good results.

That said, I can't see why a similar adjustment wouldn't increase the efficiency of any setup...

Cedrus with art999 :

www.instagram.com/p/CcLdht_IsCr/

Check the water flow behind the mast, i don't know what to think about this ? good, bad ? Any idea, theorie ?

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frenchfoiler said..
Cedrus with art999 :

www.instagram.com/p/CcLdht_IsCr/

Check the water flow behind the mast, i don't know what to think about this ? good, bad ? Any idea, theorie ?

You mean the water climbing up the mast and trailing behind?.
All masts do this to some degree, maybe with the Cedrus it is more noticeable.
Reason could be the thicker section,or the joints between the leadin&trailing edge and the carbon central part,or both.

IMHO it is drag ,lifting water takes energy,my guess is it is the result of a more turbulent vs linear flow over the mast.

Turbulent is draggier but has more energy,it might even be desirable to prevent flow separation and ventilation.But i really have not read much at all about surface piercing foils.